Implement CPU Feature selection.
The new CPUFeatures class provides feature selection based on the ID registers
in the latest (Armv8.3) Architecture Reference Manual.
This patch adds the CPUFeatures class and associated tests, but does not change
existing VIXL behaviour. Follow-up patches will add checks and assertions to the
various VIXL components.
Change-Id: I51f81b43676f7a94f406be697ca9721fd3a90fa0
diff --git a/src/cpu-features.cc b/src/cpu-features.cc
new file mode 100644
index 0000000..7843eeb
--- /dev/null
+++ b/src/cpu-features.cc
@@ -0,0 +1,206 @@
+// Copyright 2018, VIXL authors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+// this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+// * Neither the name of ARM Limited nor the names of its contributors may be
+// used to endorse or promote products derived from this software without
+// specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <ostream>
+
+#include "cpu-features.h"
+#include "globals-vixl.h"
+#include "utils-vixl.h"
+
+namespace vixl {
+
+static uint64_t MakeFeatureMask(CPUFeatures::Feature feature) {
+ if (feature == CPUFeatures::kNone) {
+ return 0;
+ } else {
+ // Check that the shift is well-defined, and that the feature is valid.
+ VIXL_STATIC_ASSERT(CPUFeatures::kNumberOfFeatures <=
+ (sizeof(uint64_t) * 8));
+ VIXL_ASSERT(feature < CPUFeatures::kNumberOfFeatures);
+ return UINT64_C(1) << feature;
+ }
+}
+
+CPUFeatures::CPUFeatures(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3)
+ : features_(0) {
+ Combine(feature0, feature1, feature2, feature3);
+}
+
+CPUFeatures CPUFeatures::All() {
+ CPUFeatures all;
+ // Check that the shift is well-defined.
+ VIXL_STATIC_ASSERT(CPUFeatures::kNumberOfFeatures < (sizeof(uint64_t) * 8));
+ all.features_ = (UINT64_C(1) << kNumberOfFeatures) - 1;
+ return all;
+}
+
+CPUFeatures CPUFeatures::InferFromOS() {
+ // TODO: Actually infer features from the OS.
+ return CPUFeatures();
+}
+
+void CPUFeatures::Combine(const CPUFeatures& other) {
+ features_ |= other.features_;
+}
+
+void CPUFeatures::Combine(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3) {
+ features_ |= MakeFeatureMask(feature0);
+ features_ |= MakeFeatureMask(feature1);
+ features_ |= MakeFeatureMask(feature2);
+ features_ |= MakeFeatureMask(feature3);
+}
+
+void CPUFeatures::Remove(const CPUFeatures& other) {
+ features_ &= ~other.features_;
+}
+
+void CPUFeatures::Remove(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3) {
+ features_ &= ~MakeFeatureMask(feature0);
+ features_ &= ~MakeFeatureMask(feature1);
+ features_ &= ~MakeFeatureMask(feature2);
+ features_ &= ~MakeFeatureMask(feature3);
+}
+
+CPUFeatures CPUFeatures::With(const CPUFeatures& other) const {
+ CPUFeatures f(*this);
+ f.Combine(other);
+ return f;
+}
+
+CPUFeatures CPUFeatures::With(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3) const {
+ CPUFeatures f(*this);
+ f.Combine(feature0, feature1, feature2, feature3);
+ return f;
+}
+
+CPUFeatures CPUFeatures::Without(const CPUFeatures& other) const {
+ CPUFeatures f(*this);
+ f.Remove(other);
+ return f;
+}
+
+CPUFeatures CPUFeatures::Without(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3) const {
+ CPUFeatures f(*this);
+ f.Remove(feature0, feature1, feature2, feature3);
+ return f;
+}
+
+bool CPUFeatures::Has(const CPUFeatures& other) const {
+ return (features_ & other.features_) == other.features_;
+}
+
+bool CPUFeatures::Has(Feature feature0,
+ Feature feature1,
+ Feature feature2,
+ Feature feature3) const {
+ uint64_t mask = MakeFeatureMask(feature0) | MakeFeatureMask(feature1) |
+ MakeFeatureMask(feature2) | MakeFeatureMask(feature3);
+ return (features_ & mask) == mask;
+}
+
+std::ostream& operator<<(std::ostream& os, CPUFeatures::Feature feature) {
+ // clang-format off
+ switch (feature) {
+#define VIXL_FORMAT_FEATURE(SYMBOL, NAME, CPUINFO) \
+ case CPUFeatures::SYMBOL: \
+ return os << NAME;
+VIXL_CPU_FEATURE_LIST(VIXL_FORMAT_FEATURE)
+#undef VIXL_FORMAT_FEATURE
+ case CPUFeatures::kNone:
+ return os << "none";
+ }
+ // clang-format on
+ VIXL_UNREACHABLE();
+ return os;
+}
+
+CPUFeatures::const_iterator CPUFeatures::begin() const {
+ if (features_ == 0) return const_iterator(this, kNone);
+
+ int feature_number = CountTrailingZeros(features_);
+ vixl::CPUFeatures::Feature feature =
+ static_cast<CPUFeatures::Feature>(feature_number);
+ return const_iterator(this, feature);
+}
+
+CPUFeatures::const_iterator CPUFeatures::end() const {
+ return const_iterator(this, kNone);
+}
+
+std::ostream& operator<<(std::ostream& os, const CPUFeatures& features) {
+ CPUFeatures::const_iterator it = features.begin();
+ while (it != features.end()) {
+ os << *it;
+ ++it;
+ if (it != features.end()) os << ", ";
+ }
+ return os;
+}
+
+bool CPUFeaturesConstIterator::operator==(
+ const CPUFeaturesConstIterator& other) const {
+ VIXL_ASSERT(IsValid());
+ return (cpu_features_ == other.cpu_features_) && (feature_ == other.feature_);
+}
+
+CPUFeatures::Feature CPUFeaturesConstIterator::operator++() { // Prefix
+ VIXL_ASSERT(IsValid());
+ do {
+ // Find the next feature. The order is unspecified.
+ VIXL_STATIC_ASSERT(CPUFeatures::kNone == CPUFeatures::kNumberOfFeatures);
+ if (feature_ == CPUFeatures::kNone) {
+ feature_ = static_cast<CPUFeatures::Feature>(0);
+ } else {
+ feature_ = static_cast<CPUFeatures::Feature>(feature_ + 1);
+ }
+ // cpu_features_->Has(kNone) is always true, so this will terminate even if
+ // the features list is empty.
+ } while (!cpu_features_->Has(feature_));
+ return feature_;
+}
+
+CPUFeatures::Feature CPUFeaturesConstIterator::operator++(int) { // Postfix
+ CPUFeatures::Feature result = feature_;
+ ++(*this);
+ return result;
+}
+
+} // namespace vixl